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C Subject  to  Revision.) 

No.  898.* 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFAC- 
TURING WORK. 

BY  WM.  S.  ALDRICH,  CHAMPAIGN,  ILL. 

(Member  of  the  Society.) 

This  paper  briefly  considers  some  essential  features  of  electric 
power  transmission  in  manufacturing  work,  t Earlier  treatment 
of  the  subject  has  been  varied  and  somewhat  scattered,  but  not 
necessarily  inadequate  as  far  as  the  science  had  been  developed  at 
the  time  of  its  presentation.  The  statements  and  principles 
here  set  forth  are  founded  upon  what  lias  been  done,  upon 
actual  experience.  Additional  and  valuable  matter  will  no 
doubt  be  brought  out  in  the  discussion  of  this  topic. 


* To  be  presented  at  the  Milwaukee  meeting  (May,  1901)  of  the  American 
Society  of  Mechanical  Engineers,  and  forming  part  of  Volume  XXII.  of  the 
Transactions. 

\ F°r  previous  discussions  on  this  topic  consult  Transactions , as  follows: 

Xo.  174,  vol.  vi.,  p.  461  Frictional  Resistance  of  Engine  and  Shafting  in 
Mills.”  J.  T.  Henthorn. 

No.  191,  vol.  vii.,  p.  138  : “ Frictional  Resistance  of  Shafting  in  Engineering 
Establishments.”  S.  Webber. 

Xo.  354,  vol.  x.,  p.  823  : “ Electric  Motors  for  Shops.” 

No.  472,  vol,  xiii.,  p.  157 : “ Electric  Power  Distribution.”  H.  C.  Spaulding.  { 
Xo.  712,  vol.  xviii.,  p.  228:  “ Friction  Horse-power  in  Factories.”  C.  H.  Benjamin. 
No.  738,  vol.  xviii.,  p.  861:  “Electricity^.  Shafting  in  the  Machine  Shop.” 
E.  H.  Benjamin. 

Xo.  746,  vol.  xviii.,  p.  1,047:  “Electrical  Power  Equipment  for  General  Factory 
Purposes,”  D.  C.  Jackson. 

No.  770,  vol.  xix.,  p.  467:  “ Electricity  in  Cotton  Mills.”  W.  B.  Smith  Whaley. 
No.  806,  vol.  xx.,  p.  435:  “ On  How  Small  a Tool  Does  it  Pay  to  Put  an  Individ- 
ual Electric  Motor,” 

No.  859,  vol.  xxi.,  p.  912  : “ Systems  and  Efficiency  of  Electric  Transmission  in 
. Factories  and  Mills.”  W.  S.  Aldrich. 


2 REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 

Examples  illustrating  one  or  more  of  the  principles  involved 
might  here  be  cited  in  detail,  but  complete  descriptions  of  in- 
stallations and  valuable  results  of  experience  are  now  accessible 
on  every  hand.  In  fact,  the  whole  development  of  this  field  of 
application  of  electricity  is  quite  open  and  above  board.  It  is 
founded  upon  common  sense  and  engineering  practice.  It  has 
therefore  at  once  an  advantage  over  many  earlier  and  some 
modern  or  wished-for  developments  of  electricity. 

The  demand  for  increased  production  is  extending  to  all  lines 
of  manufacturing  industry.  It  is  created  by  the  keen  competi- 
tion of  trade  and  the  necessity  of  filling  orders  promptly.  The 
exigencies  of  business,  therefore,  are  bringing  directly  to  the 
front  the  question  of  this  new  motive-power  in  manufacturing. 

Factories  are  not  built  in  a day,  but  the  ready  extension  of 
existing  electrical  supply  service  has  increased  the  output  from 
30  to  40  per  cent,  per  square  foot  of  floor  space.  New  machines 
and  tools  cannot  always  be  obtained  on  telegraph  order,  but  a 
resort  to  electric  driving  has  increased  the  output  of  existing 
machines  from  20  to  60  per  cent.  Workmen  may  not  be  had 
for  the  asking,  but  giving  them  electric-driven  machines  has  in- 
creased the  output  per  man  from  10  to  30  per  cent.  All  of  this 
has  been  developed  without  any  strikes  or  other  than  satisfac- 
tory regulation  of  wages  by  recognized  premium  and  price-rate 
systems. 

It  is  an  axiom  that  the  old-established  concerns  get  the  bus- 
iness. To-day  they  must  guarantee  delivery  on  time  and  at 
lower  prices  to  keep  their  factories  and  mills  in  operation. 
Electric  driving  accelerates  and  intensifies  production  for  the 
first  requirement.  It  reduces  the  cost  of  production  from  25  to 
45  per  cent  for  the  second  requirement.  Of  two  manufacturers, 
each  using  the  same  size  and  style  of  latest  machines,  with 
equally  skilled  workmen,  the  one  adhering  to  belt  transmission, 

No.  883,  vol.  xxii.,  p.  866:  “Power  and  Light  for  the  Machine  Shop  and 
Foundry.”  F.  R.  Jones. 

Special  treatment  outside  of  the  Society  Transactions  will  also  be  found  in  : 

“ Western  Society  of  Engineers,  Chicago,”  June,  1898,  vol.  iii. , Transactions. 
“American  Institute  Electrical  Engineers,”  1899,  vol.  xvi.,  Transactions. 

“ Institution  of  Electrical  Engineers,  London,”  Journal,  July,  1900;  vol.  xxix., 
Transactions. 

“ Railway  Master  Mechanics  Association,  Report  by  Committee,”  Railway  Master 
Mechanic,  June-July,  1900  ; Engineering  News,  July  12,  1900. 

“ Franklin  Institute,  Philadelphia,”  January,  1901,  vol.  151,  Journal. 


a t\  c.Ki  <2  \ ^ C*\ 


) 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 


with  its  limited  capacity  and  speeds,  will  probably  fall  behind 
in  orders.  With  many  manufacturers  it  is  still  a question 
whether  the  electric  drive  costs  more  to  install  and  to  maintain 
than  the  belting  system.  This  can  only  be  determined  for  each 
particular  case  as  it  arises.  If  it  should  cost  more,  it  will  still 
prove  a profitable  investment  when  it  increases  the  output  per 
day,  per  man,  per  machine,  per  square  foot  of  floor  space,  in- 
creasing the  quantity  and  enhancing  the  quality  of  the  product 
while  decreasing  the  cost. 

It  is  no  longer  a question  of  the  efficiency  of  electricity  vs.  shaft- 
ing for  power  transmission.  Nor  is  it  a mere  question  of  saving 
at  the  coal  pile  when  only  2 or  3 per  cent,  of  the  total  cost  of 
production  is  to  be  charged  to  the  fuel  account.  In  many  cases 
electricity  has  effected  a saving  during  the  first  year  that  has 
more  than  paid  for  the  change  to  the  new  system.  Whether  it 
is  more  or  less  economical  than  mechanical  transmission  depends 
upon  circumstances.  When  properly  installed  and  operated, 
electricity  should  have  inherently  all  of  the  considerations  in 
its  favor. 

The  resulting  economy  of  production  and  the  ability  to  fill 
orders  promptly  are  all  in  favor  of  the  electric  system.  It  may 
be  compared  to  skilled  labor, — high-priced,  but  very  desirable 
^ from  the  standpoint  of  the  economics  of  production.  Few  man- 
ufacturers still  hesitate  to  employ  high-priced  skilled  labor. 
J Many  more  cling  to  antiquated  methods  of  driving  modern 
~ piacliinery  operated  by  most  skilful  workmen.  To-day,  there- 
fore, this  question  assumes  very  different  proportions.  The 
^discussion  has  been  shifted  to  the  field  of  manufacturing 
economics,  involving  considerations  of  maximum  output  with 
given  equipment,  floor  space  and  working  force.  It  is  a question 
of  accepting  and  filling  orders  or  of  losing  the  business  to  those 
manufacturers  who  can  take  them. 

The  disciplinary  value  of  electric  driving  cannot  be  ignored. 
The  old  easy-going  belt  system  used  to  allow  many  a glance  at 
the  morning  news,  many  a familiar  chat  during  long  and  deep 
cuts.  With  the  electric  drive  the  operator  finds  it  very  conven- 
ient to  be  near  his  machine.  The  customary  warning  signals  of 
slipping  belts  are  no  longer  heard. 

Satisfactory  illumination  should  also  be  provided.  No  one 
will  work  by  a smoky  torch  when  he  can  have  ah  arc  or  an 
incandescent  lamp.  Electric  light  must  be  supplied  in  these 


; 


I REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 

times  in  all  shops  where  they  make  a practice  of  doing  a day’s 
work  the  year  round.  Only  a little  wiring  is  required,  and  a 
small  amount  of  extra  power  is  necessary  at  the  generating  plant 
to  drive  machines  and  tools  by  electricity.  In  many  instances 
electric  lighting  has  paved  the  way  for  electric  driving. 

We  have  all  had  experience  in  getting  men  to  “ speed  up  ” their 
machines.  Tradition  and  custom  are  both  against  the  operator 
who  does  much  belt  shifting.  In  the  eyes  of  almost  all  journey- 
men and  of  some  piece  workers  it  is  next  to  treasonable  to  change 
the  rate  of  working.  Even  though  paid  extra,  to  do  more  than  a 
day’s  work  in  many  shops  is  still  a crime  against  the  union  or 
other  combination  interested.  The  workman  who  attempts  it 
soon  finds  a job  elsewhere  or  is  promoted.  The  electric  drive 
changes  all  of  this.  A press  of  the  button,  a turn  of  the  lever, 
and  each  piece  of  work  can  be  executed  at  maximum  speeds 
allowed  by  the  temper  of  the  tool  steel.  It  forcibly  illustrates 
Maxim’s  statement  that  American  workmen  find  it  pays  to  do  as 
much  as  they  can. 

The  ever-widening  applications  of  electricity  in  manufacturing- 
work  show  that  it  has  fully  proven  its  claim  to  a consideration. 
It  is  thoroughly  reliable.  It  has  come  to  stay.  It  fills  the  exacting 
requirements  in  this  new  field  more  economically  and  satisfactor- 
ily than  any  other  system  of  power  transmission.  In  the 
common  forward  movement  of  industry  electricity  is  still  in 
the  van.  It  stands  ready  for  any  emergency  within  its  province 
and  so  far  has  been  equal  to  each  new  demand  made  upon  it. 

Aside,  however,  from  all  purely  technical  considerations  of 
the  application  of  electricity  to  manufacturing  stands  pre- 
eminently the  question  : does  it  pay  ? Many  manufacturers 
have  conclusively  shown  that  the  economies  of  production  have 
been  enhanced  by  their  adoption  of  electricity,  that  its  inherent 
advantages  in  this  relation  far  outweigh  all  previously  debatable 
questions  of  economy  and  efficiency  of  the  electric  drive  com- 
pared with  belting  transmission  and  that  even  if  there  were  no 
saving  at  the  coal  pile  it  would  still  not  pay  to  return  to  the  old 
method  and  lose  orders. 

I. — General  Considerations. 

1.  Electric  Transmission  in  Manufacturing  Work  is  a Means  to 

an  End : Centralized  power  generation  for  light  and  manufac- 
turing purposes ; subdivision  of  the  transmission  system  and 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 


5 


the  motive-power  equipment ; execution  of  all  classes  of  work, 
irrespective  of  its  location ; maximum  efficiency  of  workmen, 
machines  and  labor  involved ; intensified  production  at  best 
speeds  and  at  the  power  limit  of  machines  with  improved  quality, 
maximum  output  and  reduced  cost. 

2.  Sanitary  Considerations : It  is  healthful,  clean,  and  free  from 
dirt,  dust  and  dripping  oil ; it  affords  accommodations  and  facili- 
ties for  proper  lighting  and  ventilation  ; it  removes  dangers  from 
overhead  machinery  shafting  and  belts  ; it  reduces  the  sick  list 
to  a minimum  ; it  insures  quietness  from  absence  of  much  un- 
necessary noise  with  older  systems,  and  develops  cheerfulness  in 
workmen. 

3.  Disciplinary  Value : It  improves  the  morale  and  the  person- 
nel of  workmen  ; it  conduces  to  shop  order  and  discipline,  with 
the  most  economic  use  of  the  workman’s  time,  quick  handling  of 
material  and  maximum  efficiency  of  labor. 

4.  Flexibility  of  the  System  : Accessibility  of  all  parts,  adapta- 
bility to  various  uses,  and  portability  of  tools  are  inherent 
advantages. 

5.  Reliability  of  Service : It  is  free  from  any  general  breakdown, 
localizing  casualties  and  stopping  least  machinery  for  repairs  ; 
no  accident  can  affect  the  whole  plant  in  any  case  of  a modern 
electrical  installation  properly  designed,  equipped,  and  oper- 
ated ; it  is  more  to  be  depended  upon  than  any  other  system. 

II.  Economics  of  Electricity  in  Manufacturing. 

1.  Electric  Power  Generation  : This  system  admits  of  central- 
ized or  concentrated  power  generation  which  is  required  for 
maximum  economy.  Distributed  power  generation  in  small  and 
scattered  units  is  very  wasteful. 

The  electric  power  plant  may  be  located  to  best  advantage 
for  fuel  and  water  supplies,  conveying  and  transportation  facili- 
ties. It  may  be  isolated  from  other  structures,  so  reducing  fire 
risks  and  insurance  rates,  especially  where  the  boiler  house  is 
in  a separate  building. 

The  electric  generating  sets  may  be  subdivided  into  similar 
and  independent  units.  These  may  be  operated  at  all  times 
under  the  most  economic  condition  of  normal  loads.  This 
permits  manufacturing  work  in  any  branch  or  section  of  the 
establishment  as  economically  under  part  load  as  under  full 


6 REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 

load,  on  overtime  and  night  shifts  as  during  the  day’s 
work. 

Electric  light  may  be  supplied  from  the  power  mains  or  from 
separate  generators,  as  conditions  require.  In  not  a few  cases 
of  the  introduction  of  electric  driving  the  additional  saving 
has  been  more  than  enough  to  pay  for  all  of  the  lighting  ser- 
vice. 

The  cost  of  generating  electric  power  can  only  be  a deciding 
factor  when  the  total  cost  of  power  required  is  large  compared 
to  the  running  expense.  The  saving  in  fuel  depends  upon  the 
cost  of  fuel,  the  average  load,  the  amount  of  shafting  and  belt- 
ing displaced. 

2.  Electric  Power  Transmission : The  distances  are  short  in 
factory  service,  the  electric  distribution  being  within  one  build- 
ing or  a group  of  buildings.  The  so-called  line  losses  are  there- 
fore usually  negligible  in  well-designed  installations.  Low 
voltages  are  employed  in  factory  transmission.  From  110  to 
550  volts  are  the  accepted  limits  at  the  present  time  in  this 
country,  either  for  direct-  or  alternating-current  working  at 
constant  potential  or  pressure.  The  economics  of  the  various 
systems  can  be  only  satisfactorily  discussed  with  reference  to  any 
given  project  or  installation. 

The  following  are  recognized  methods  of  distribution,  for 
electric  light  or  power,  or  both,  in  manufacturing  work  : 

Two-wire  and  tliree-wire  systems,  for  direct  or  alternating 
currents. 

Multi-circuit  system  for  direct-current  multi- voltage  service. 

Single-phase,  two-wire  alternating  current. 

Two-phase,  three-  or  four- wire  alternating  current. 

Three-phase,  three-  or  four-wire  alternating  current. 

Composite  system,  direct  current  and  single-phase  or  two- 
phase  alternating  current  on  the  same  wires. 

3.  The  First  Cost  of  Electrical  Installation  : This  will  usually  be 
higher  for  an  electrical  than  for  a mechanical  transmission. 
The  interest  on  first  cost  will  rarely  be  a determining  factor. 
It  will  be  more  than  offset  by  the  manufacturing  economies 
elsewhere  effected  and  by  the  reduced  cost  of  shop  buildings 
incident  to  the  use  of  the  electric  drive. 

4.  Maintenance  of  Electric  System : The  cost  of  maintenance  is 
a minimum.  The  depreciation  is  less  than  in  any  other  system. 

The  saving  effected  is  much  more  than  sufficient  to  pay  for  all 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK.  7 

of  the  incidental  repairs  and  renewals  to  the  electrical  machin- 
ery or  the  wiring  system. 

Attendance  and  supervision  are  largely  centralized  and  re- 
duced to  a minimum  compatible  with  efficient  service,  owing  to 
the  reliability  of  the  system. 

Electric  generators  and  motors  are  the  simplest  types  of  mo- 
tive-power machinery  that  can  be  used  in  the  development  of 
power  transmission  for  manufacturing  work.  They  have  the 
fewest  parts  requiring  any  renewals.  They  require  practically 
no  repairs. 

Electric  machines  will  either  work  or  not  work.  They  soon 
make  their  wants  known.  They  cannot  be  maintained  in  waste- 
ful operation,  as  is  the  case  with  every  other  kind  of  motive- 
power  machinery.  Standardization  of  this  class  of  electrical 
machinery  has  facilitated  repairs.  They  are  quickly  and  easily 
made,  at  minimum  cost  and  with  least  interference  with  the 
routine  work  of  the  establishment.  Small  electric  motors  in 
general  require  more  frequent  attention  and  renewals  than  larger 
machines. 

Belt  tightening  or  lacing  in  the  old  system  stops  work  on 
that  secton,  and  stops  all  work  if  it  chances  to  be  the  main  driv- 
ing belt.  Any  similar  casualty  in  the  electric  system  is  reme- 
died at  once  by  throwing  into  service  another  line,  or  a jumper, 
or  a relay  bus-bar. 

III.  Influence  of  Electric  Transmission  upon  Factory 

Buildings. 

The  design,  plan,  and  arrangement  of  manufacturing  estab- 
lishments are  not  now  dictated  or  controlled  by  the  new  electric 
transmission,  as  always  has  been  the  case  with  the  old  mechani- 
cal system.  Factory  and  mill  construction  is  undergoing  radi- 
cal changes  incident  to  the  electric  transmission  of  power. 
There  is  now  a superior  adaptation  of  the  building  to  manufac- 
turing work  and  sanitary  requirements,  with  higher  ceilings  for 
light,  ventilation,  and  overhead  transportation.  The  cost  of 
buildings  is  reduced  to  a minimum.  The  electric  drive  does  not 
require  the  heavy  construction  of  walls,  overhead  work,  and  roof 
trusses  demanded  by  shafting  transmission. 

The  site  for  buildings  may  be  chosen  independent  of  power 
considerations  and  located  on  most  suitable  ground.  There  is 
no  necessity  for  buildings  being  placed  around  or  adjacent  to 


8 REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 

tlie  power-house,  as  required  for  mechanical  connections  to  en- 
gines or  turbines.  Grouped  shops  may  be  arranged  in  best 
manner  to  facilitate  economic  production  and  the  handling,  con- 
veying, and  transportation  of  material  and  work.  Detached 
buildings,  a tendency  of  certain  lines  of  modern  manufacturing 
development,  are  feasible  and  the  work  therein  facilitated  by 
electric  transmission.  The  isolation  of  various  shops,  depart- 
ments, and  workrooms  for  manufacturing  or  insurance  reasons 
may  be  carried  to  any  extent  with  the  electric  system  without 
impairing  its  efficiency  or  economy.  The  output  per  square 
foot  of  floor  space  is  a maximum  with  electric  transmission. 

IY.  Influence  of  Electric  Transmission  upon  Workshop 

Expansion. 

Future  areas  of  work  may  be  planned  and  arranged  for  with 
the  utmost  freedom  and  entirely  irrespective  of  power  consider- 
ations. They  can  be  located  as  desired,  on  separate  floors,  in 
various  departments  or  in  detached  buildings.  Original  pro- 
vision for  prospective  development  is  not  necessary  in  the  elec- 
tric system,  but  is  required  by  shafting  transmission.  There  is 
no  expense  for  contemplated  additions  till  they  are  actually  in- 
stalled as  required. 

Permanent  additions  to  the  electric  generating  plant  and  the 
distributing  system  are  made  with  a gradual  and  pro  rata  out- 
lay of  capital,  instead  of  in  disproportionate  blocks  of  new 
equipment,  as  required  by  mechanical  transmission. 

Extensions  of  electric  transmission  and  new  centres  of  power 
distribution  may  be  established  at  any  time  and  of  reasonable 
capacity,  anywhere  and  at  any  distance,  at  minimum  cost  for 
labor  and  material.  There  is  no  crowding,  overloading,  or  in- 
terference with  existing  conditions,  or  with  the  daily  progress 
of  routine  work.  Temporary  extensions,  to  meet  sudden  de- 
mands for  power  at  any  point,  are  quickly  made  by  running  to 
the  desired  location  electric  wires  or  cables.  These  are  easily 
removed  when  no  longer  required  and  as  readily  used  elsewhere 
for  similar  purposes.  The  shifts  are  made  with  the  least  ex- 
pense of  time  and  labor  in  handling,  and  with  no  accompanying 
waste  of  material  to  suit  different  conditions. 

Auxiliary  power  is  always  at  hand  for  emergencies  and  to 
almost  any  reasonable  extent,  on  account  of  the  reserve  nature 
of  the  electric  supply. 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK.  9 


Y.  Influence  of  Electric  Drive  upon  Arrangement  of 

Machinery. 

The  floor  space  required  per  machine  or  tool  is  reduced  to  a 
minimum. 

The  alignment  of  overhead  shafting  is  no  longer  necessary. 

Clear  overhead  room  is  provided  for  handling  all  classes  of 
heavy  work.  The  crowding  and  complications  arising  from 
overhead  shafts  and  belts  are  avoided. 

Location  of  machines  and  tools  may  be  made  to  suit  the  re- 
quirements of  the  work  and  the  available  floor  space.  The 
product  may  then  be  finished  with  least  time  and  labor,  with 
least  handling  and  transportation,  and  in  the  most  efficient  and 
economic  manner. 

All  the  conditions  of  work  and  of  labor  may  be  arranged  to 
handle  tools  and  material  to  the  best  advantage  with  freedom 
of  workman’s  movements  and  facility  in  executing  manufactur- 
ing operations. 

YI.  Changing  from  the  Old  to  the  New  System  of  Driving. 

When  alterations  or  additions  in  power  transmission  are  re- 
quired, it  is  the  invariable  practice  in  many  modern  shops  to 
extend  in  the  line  of  electric  driving.  This  is  notably  the  rule 
where  electric  supply  is  already  at  hand  for  either  lighting  or 
power  service.  In  the  rehabilitation  of  an  old  establishment 
some  of  the  shafting  transmission  may  usually  be  combined 
with  the  electric  drive,  as  in  the  so-called  group  system.  Much 
can  be  done  to  improve  the  power  transmission  if  existing  lines 
of  shafting  are  divided  into  the  most  economic  sectional  lengths, 
determined  by  the  speed,  character  of  load,  and  kind  of  work. 
Electric  motors  will  prove  valuable  adjuncts  if  installed  to  drive 
these  sections  independently.  The  electric  drive  is  an  economic 
and  flexible  auxiliary,  supplementing  the  earlier  and  rigid  me- 
chanical power  transmission.  Such  partial  introduction  of  the 
new  system,  especially  if  an  electric  lighting  plant  is  already  in 
service,  will  early  develop  its  advantages.  It  will  defray  the 
cost  of  installation  and  maintenance  by  greater  economic  pro- 
duction. 

Scrapping  the  old  to  make  room  for  the  new  involves  the 
same  economic  questions  in  the  case  of  power  transmission  as 
in  that  of  manufacturing  machinery.  Productive  machinery 


10  REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 


should  not  in  general  be  scrapped  while  there  is  retained  the 
old  system  of  belt  driving,  with  its  inherent  power  and  speed 
limitations.  The  increased  output  of  the  old  machine,  elec- 
trically driven,  will  frequently  equal  that  of  a new  machine, 
belt  driven,  and  turning  out  the  same  kind  of  product. 

VII.  Application  of  the  Electric  Drive. 

1.  Individual  Driving  Without  Intermediate  Gearing : The 

armature  of  the  motor  is  mounted  on  the  main  spindle  of  the 
machine.  The  power  is  most  directly  applied,  with  ideal  adap- 
tation of  tool  to  work. 

It  requires  more  or  less  special  adaptation  of  motor  to  ma- 
chine, with  rarely  any  marked  changes  in  the  structural  design 
of  the  latter. 

2.  Individual  Driving  with  Intermediate  Gearing : The  motor 
is  conveniently  mounted  on  the  frame  of  the  machine  and  drives 
it  through  the  intervention  of  the  ordinary  gearing. 

It  requires  no  special  adaptation  of  motor  to  machine.  Any 
suitable  motor  may  be  used  on  any  machine. 

3.  Advantages  of  the  Individual  Drive : The  workman  has  the 
most  perfect  control  of  all  factors  entering  into  the  economics 
of  production.  There  is  maximum  economy  in  the  application 
of  power. 

The  speed  control  and  the  output  are  independent  of  any 
other  machine.  They  are  no  longer  limited  by  the  speed  of  the 
line  shafting.  Machines  and  tools  may  now  be  worked  to  the 
limits  of  their  respective  capacities. 

The  productive  efficiency  of  the  machine  is  increased.  It 
may  be  operated  at  all  times  up  to  the  power  limit,  reducing 
time  and  cost  of  labor  for  any  given  product. 

The  choice  of  the  individual  drive  depends  upon  the  power 
required,  the  size  of  the  machine,  the  time  it  is  in  service,  and 
the  value  of  the  product. 

The  individual  motor  drive  is  usually  adopted  where  the  ma- 
chine is  in  use  only  part  of  the  time,  and  in  sizes  as  small  as 
two  or  three  horse-power,  and  requiring  wide  variations  in 
speed  and  power  for  maximum  output  quite  independent  of  the 
first  cost.  For  large  machines  this  method  reduces  the  power 
losses  to  a minimum.  It  is  particularly  advantageous  for  shears, 
punches,  and  a class  of  repair  shop  tools  requiring  power  only 
at  intervals.  The  constructive  details  and  design  of  direct- 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK.  11 

driven  machines  are  not  usually  altered  to  any  extent ; second- 
ary speed  changes  are  obtained  by  the  usual  change-gear  and 
mechanism  ; in  special  cases  of  large  tools,  a range  of  speeds  is 
sometimes  best  provided  by  a special  variable-speed  motor. 

4.  Group  Driving : A few  large  electric  motors  are  employed 
independently  driving  sections  of  shafting  of  most  economical 
length.  This  method  is  thus  adapted  for  driving  a number  of 
small  machines,  with  no  particular  requirements  in  speed  or  in 
power  ; or  for  niQst  economical  manufacturing  along  special 
lines ; or  for  driving  any  section  on  overtime  or  night  shifts  ; 
or  for  independent  driving  of  separate  floors,  departments,  or 
detached  buildings. 

The  maximum  economy  with  the  group  system  can  only  be 
secured  when  all  of  the  machines  so  driven  are  in  constant  use, 
at  best  speeds  for  maximum  output.  This  dictates  grouping 
machines  as  far  as  practicable  of  the  same  size,  style,  functions, 
speed  and  power  requirements,  having  due  regard  to  the  work 
to  be  executed.  Sectionalizing  the  power  transmission  by  sub- 
stituting electric  motors  for  either  the  main  or  section  belts 
secures  partial  advantages  of  the  new  system  side  by  side  with 
the  old,  and  is  frequently  resorted  to  in  old  establishments 
adopting  new  methods. 

5.  Individual  and  Group  Driving  : The  most  general  require- 
ments of  factory  transmission  can  all  be  met  by  an  intelligent 
combination  of  these  two  methods  of  electric  driving. 

The  first  cost  of  installing  the  individual  drive  will  generally 
be  from  2 to  5 per  cent,  higher  than  for  the  best  group 
system,  when  all  other  considerations  are  the  same.  The  in- 
dividual drive  is  more  economical  in  the  use  of  power  than  the 
group  system,  especially  if  in  the  latter  only  a limited  number 
of  grouped  machines  are  in  use  at  any  one  time,  at  average 
loads. 

6.  Portable  Tools  and  Appliances : The  extreme  flexibility  of 
the  electric  system  invites  the  widest  use  of  portable  tools  and 
appliances.  A flexible  heavily-armored  cable  gives  any  desir- 
able radius  of  action,  with  no  expense  to  maintain  as  a part  of 
the  transmission  system,  with  no  danger  or  difficulty  in  hand- 
ling, and  requiring  least  time  and  labor  for  any  immediate  shift- 
ing of  tool  or  work.  Least  used  tools  need  not  occupy  floor  space 
when  not  in  operation.  Most  favorable  economic  relations  may, 
therefore,  be  secured  in  many  lines  of  manufacturing  work, 


12  REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 


especially  of  the  heavier  grades.  Almost  all  required  tools  may 
be  taken  to  and  operated  at  the  work  in  hand.  Time  is  saved 
in  not  having  to  shift  and  adjust  the  work  to  the  machine  or 
tool.  Several  operations  may  be  carried  on  at  one  time  by 
bringing  different  tools  to  the  work,  each  independently  driven 
and  operated. 

7.  Electric  Transportation  and  Conveying : Electric  hauling  by 
surface  or  overhead  systems  of  distribution,  electric  conveying 
and  telpher  systems,  electric  cranes,  hoists,  lifts,  and  elevat- 
ors, are  all  well-developed  fields,  and  present  no  unusual  nor  in- 
surmountable difficulties  when  installed  as  a part  of  the  regular 
electric  system  of  a manufacturing  establishment.  Tools  are 
taken  to  the  work,  or  machines  and  tools  are  quickly  served 
with  material  and  work,  reducing  the  cost  of  all  handling  to  the 
lowest  terms  in  a field  of  non-productive  labor  that  has  formerly 
been  very  expensive. 

8.  E lectric-I) riven  Auxiliaries:  With  an  established  electric 
supply  service  for  all  manufacturing  work  it  is  an  economic  step 
to  drive  by  electricity  all  auxiliaries,  as  pumps,  fans,  blowers, 
air  compressors,  etc. 

VIII.  Selection  of  Equipment. 

1.  Factors  Determining  Choice  of  the  Electric  System:  Each 
manufacturing  industry  has  its  own  inherent  requirements. 
No  general  rules  can  be  given,  but  every  case  must  of  necessity 
be  studied  and  developed  by  itself  with  a thorough  preliminary 
survey  of  all  conditions  and  requirements.  One  successful  sys- 
tem cannot  furnish  precedent  for  another. 

In  general,  the  following  lines  of  inquiry  should  be  freely  in- 
vestigated before  choosing  any  system  for  power  transmission 
in  manufacturing  work  : the  size  of  the  establishment ; the  area 
to  be  served  ; the  arrangement  and  grouping  of  shops,  depart- 
ments or  buildings ; the  arrangement,  types,  and  sizes  of  ma- 
chines or  tools  to  be  driven ; the  variety  of  speeds  required ; 
the  character  of  the  loads  involved ; the  kind  of  work  to  be 
executed ; the  economics  of  fuel  and  water  supplies. 

The  above  items  should  have  been  predetermined  from  the 
standpoint  of  most  economic  production.  They  should  in  no 
wise  be  influenced  by  questions  of  power  transmission.  How 
to  drive  the  machinery  in  anew  and  modern  manufacturing  plant 
should  be  a second  and  not  a first  consideration.  It  should  be 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK.  13 


determined  by,  ratlier  than  itself  determine,  the  conditions  for 
economic  production. 

2.  Interchangeability  Throughout  the  Electric  System:  It  should 
be  possible  to  drive  similar  apparatus  and  motors  from  any 
point  of  attachment  to  the  wiring  system.  Greater  flexibility 
is  thereby  secured,  added  facilities  provided  for  use  of  portable 
tools,  and  readiest  extension  made  of  plant  and  distributing 
system  at  any  time.  Preferably  have  one,  and  only  one,  electric 
system  if  it  can  be  secured  by  intelligent  consideration  of  all 
present  and  the  most  probable  future  requirements.  This  does 
not  necessarily  imply  that  it  is  best  to  have  one  single  circuit 
for  all  kinds  of  service  required  in  a manufacturing  establish- 
ment, as  light  and  power ; but  it  should  not  be  required  to  use 
different  circuits  for  the  same  service,  as  portable  tools. 

3.  Uniformity  of  Electrical  Equipment:  Generating  sets  and 
motor  equipments  should  be  standardized  as  far  as  possible  in 
the  case  of  any  given  establishment.  These  machines,  as  well 
as  all  their  parts,  should  be  readily  obtained  in  duplicate  at  any 
time.  This  is  particularly  important  in  making  additions  and 
extensions  in  the  group  system,  where  it  may  be  required 
to  change  from  a smaller  to  a larger  motor  at  any  time  to 
accommodate  more  machines  on  a given  section.  It  cannot  be 
advantageous  to  experiment  with  different  styles  and  types. 
Electrical  machinery  to-day  is  so  far  standardized,  and  its  per- 
formance predetermined,  that  there  can  be  no  excuse  for  not 
selecting  that  style  and  type  best  adapted  to  any  given  factory. 

4.  Power  Required  as  a Basis  for  Size  of  Electric  Motor : The 
load  diagram  for  any  machine  will  furnish  the  best  data  for 
determining  the  proper  size  of  motor.  It  may  be  readily  ob- 
tained under  the  working  conditions  of  the  machine  by  using  a 
test  motor. 

In  almost  all  metal-working  industries  the  power  required  is 
subject  to  extreme  fluctuations,  and  may  be  very  heavy,  at 
times,  while  the  bulk  of  it  will  be  quite  light.  It  is  not  neces- 
sary to  install  an  electric  motor  to  carry,  for  any  length  of  time, 
such  sudden  and  heavy  loads  as  will  be  shown  by  the  peaks  of 
the  load  diagrams  for  the  several  machines,  or  the  sudden 
initial  throw  of  the  ammeter  needle. 

The  limit  of  overload  is  fixed  by  the  allowable  rise  of  tem- 
perature, and  can  readily  be  predetermined  for  any  given  elec- 
tric motor.  In  general,  the  surface  temperature  of  the  motor 


14  REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 

field  coils,  as  measured  by  a thermometer,  should  not  exceed 
from  35  to  45  degrees  C.,  with  a maximum  limit  of  50  degrees  C., 
after  an  overload  run  of  from  six  to  eighteen  hours,  as  may  be 
specified  by  the  builders. 

Starting  load  currents  are  of  course  high,  and  may  be  from 
two  to  three  times  the  normal  current,  as  in  the  case  of  over- 
loads, for  brief  periods.  Individual  drives  require  proportion- 
ately larger  motors  to  enable  them  to  carry  alone  the  heavy 
overloads.  Group  drives  require  only  normal  load  motors,  as 
it  will  rarely  ever  occur  that  the  several  grouped  machines  are 
all  carrying  overloads  at  the  same  instant.  Motors  for  this  ser- 
vice may  often  be  much  smaller  than  would  be  dictated  by  the 
combined  load  diagram  of  the  machines  forming  the  given  group 
or  section.  In  no  case  will  they  require  to  approach  the  maxi- 
mum, or  the  sum  of  the  maximum,  loads  of  the  various  ma- 
chines. Group  system  load  curves  will  be  smoothed  out  con- 
siderably. In  all  electric  motor  installations  there  should  be 
ample  power  provided,  rather  than  a narrow  margin  only  to 
work  upon.  Increasing  loads  are  almost  sure  to  arise  in  time. 
A motor  of  ample  size  gives  that  reserve  power  so  character- 
istic of  the  electric  system,  if  properly  installed. 

5.  Character  of  Loads  in  Manufacturing  Work : Load  curves 
and  diagrams  of  individual  machines,  groups,  sections,  and  the 
entire  plant,  only  can  be  relied  upon  in  estimating  the  charac- 
ter of  loads  being  carried  or  likely  to  be  carried  under  simi- 
lar conditions.  The  load  factor,  the  ratio  of  the  maximum  to 
the  average  load,  for  any  given  time  on  any  part  of  the  system, 
should  be  as  high  as  possible  for  best  working  efficiency  and 
economy.  It  may  be  largely  influenced  by  the  way  the  oper- 
ator handles  his  motor.  Whatever  the  kind  of  load,  uniform  or 
variable,  light  or  heavy,  continuous  or  intermittent,  suddenly 
fluctuating  or  periodically  variable,  it  must  be  carefully  inves- 
tigated before  installing  electric  motive-power.  In  certain  in- 
stances flywheels  may  be  useful  and  for  the  same  mechanical 
reasons  as  elsewhere  employed  in  machinery. 

6.  Speeds  of  Manufacturing  Machinery : The  speeds  should  be 
predetermined  by  the  conditions  for  most  economic  maximum 
output,  and  so  fix  the  range  required  for  the  electric  motors. 
In  no  instance  should  the  reverse  be  the  case.  In  many  cases 
of  individual  drives  it  may  be  best  to  secure  the  speed  reduc- 
tions mechanically,  as  by  the  ordinary  change-gear.  It  is  not 


REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK.  15 

necessary  nor  advisable  in  all  cases  to  secure  the  same  by 
mounting  the  motor  armature  directly  on  the  spindle  of  the 
machine.  Provide  motors  with  speeds  consistent  with  the  range 
of  change-gear,  and  gear  down  rather  than  up. 

7.  Electric  Generators  Required  in  Manufacturing  Plants : The 
style  and  type  should  be  largely  determined  by  the  kind  of  ser- 
vice to  be  supplied,  the  size  by  the  normal  and  overload  condi- 
tions as  shown  by  the  plant  load  diagrams,  with  due  considera- 
tions given  to  special  conditions  and  variable  loads. 

The  actual  normal  capacity  of  the  generator  will  be  chiefly 
determined  by  the  length  of  time  the  various  motors  are  in  use, 
rather  than  by  their  normal  or  aggregate  capacity.  It  may  hap- 
pen, owing  to  the  intermittent  use  of  machines  and  motors,  that 
the  generating  plant  may  be  reduced  to  50  per  cent.,  or  even  to 
20  per  cent,  of  the  aggregate  normal  capacity  of  the  motors  out 
in  the  establishment.  An  increase  of  the  electrical  system  can 
only  be  intelligently  made  from  a careful  study  of  the  load 
curves  of  the  existing  installation,  and  using  it  as  a basis  for 
comparison  with  the  probable  load  curve  under  the  proposed 
conditions.  There  should  be  judicious  subdivision  of  the  gen- 
erating plant  into  units,  preferably  of  the  same  size  and  style, 
that  they  may  be  readily  interchanged  and  duplicated  at  any 
time,  with  one  • or  two  relay  units  for  emergencies  and  extra 
rush  seasons  of  work.  All  generating  units  used  in  manufactur- 
ing installations  will  necessarily  be  of  such  size  as  to  warrant 
their  being  driven  by  direct  connection  to  engines  or  turbines. 
If  generators  required  are  too  small  to  warrant  direct  connec- 
tion, the  establishment  is  too  small  to  warrant  an  introduction 
of  the  electric  drive. 

8.  The  Electric  Wiring  and  Distributing  System : All  wiring 
should  be  done  in  accordance  with  the  “National  Electric  Code,” 
being  the  rules  and  requirements  of  the  National  Board  of  Eire 
Underwriters.  Separate  service  circuits,  from  the  same  or  sepa- 
rate bus-bars,  may  be  provided  to  advantage,  for  lighting  and 
various  power  uses.  Sub-stations,  or  sub-station  switchboards, 
should  be  provided  for  separate  shops,  floors,  departments,  or 
buildings,  making  it  unnecessary  to  run  a separate  set  of  wires 
back  to  main  switchboard  for  each  service. 

9.  Indirect  Electric  Distribution : Indirect  distribution,  through 
the  use  of  accumulators,  converters,  or  transformers  may  be 
found  expedient  under  certain  conditions.  Eor  the  three-wire 


16  REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 

systems,  some  type  of  accumulator  or  motor-generator  balanc- 
ing set  is  almost  essential  for  efficient  regulation.  The  accu- 
mulator may  render  as  invaluable  service  in  certain  kinds  of 
factory  installations,  as  in  iron  and  steel  mills,  as  it  is  now  ren- 
dering traction  work,  where  the  character  of  the  load  variations 
of  the  former  is  somewhat  analogous  to  that  of  the  latter.  The 
loss  in  the  battery  is  very  small  and  entirely  negligible  com- 
pared to  the  advantages  to  be  derived  from  its  use  in  manufac- 
turing plants  of  the  type  mentioned. 

IX.  Losses  in  Factory  Transmission. 

The  inherent  losses  common  to  all  systems  of  factory  trans- 
mission are  due  to  the  intermittent  and  irregular  use  of  the 
machines  driven.  These  are  reduced  to  a minimum  with  the 
electric  drive.  There  is  no  consumption  of  power  when  the 
motor  and  machine  are  not  in  operation.  There  are  no  power 
losses  when  the  motor  is  not  in  use,  no  so-called  dead  load 
losses,  due  to  • mechanical  friction  of  the  shafting  system,  no 
transmission  losses  in  the  line  when  the  electric  current  is  not 
required. 

Electric  generators  and  motors,  when  in  operation  at  uniform 
speeds,  have,  generally  speaking,  but  two  kinds  of  losses : the 
first  is  a constant  quantity  depending  upon  the  size  and  type  of 
machine  ; the  second  is  a variable  loss  proportional  to  the  square 
of  the  current  in  the  armature  circuit.  The  electric  line  and 
other  wiring  has  a loss  proportional  to  the  square  of  the  cur- 
rent carried.  The  cost  of  waste  power  in  the  mechanical  sys- 
tem becomes  excessive  at  light  and  frictional  loads.  It  is  saved 
in  the  electric  system,  in  which  the  constant  losses  are  mini- 
mized and  the  variable  losses  are  throughout  proportional  to 
the  amount  of  work  being  done. 

X.  Efficiency  of  Electric  Transmission. 

The  efficiency  of  the  electric  system  under  normal  conditions 
shows  high  maintained  values,  from  about  25  to  35  per  cent, 
underload  to  the  same  amount  of  overload,  for  the  individual 
generators  and  motors,  as  well  as  for  the  aggregate  efficiency  of 
the  installation.  In  mechanical  transmission  there  is  a con- 
stant falling  off  in  efficiency  at  various  underloads  in  every  part 


( 


^REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK.  17 

of  the  system,  owing  fcTthe’inherent  losses  duejto  mechanical 
friction,  which  losses  are  constant  at  all  loads  and  constant 
speeds.  It  is  not  ^question  so  much  of  the  individual  efficien- 
cies, in  either  case,  as  of  the  aggregate  or  combined  efficiency, 
from  engine  or  turbine  shaft  to  machine  or  tool.  The  perform- 
ance should  be  considered  and  compared  at  proportional  parts 
of  the  full  load  as  well  as  at  normal  loads.  The  mechanical 
efficiency  of  all  manufacturing  machines  is  almost  invariably  low. 
It  is  possible  materially  to  effect  it  by  efficient  motors  properly 
selected,  installed,  and  operated. 

The  all-day  efficiency  may  be  made  higher  with  the  electric 
drive  than  with  any  other  system,  as  the  amount  of  time  is  mini- 
mized during  which  machines  and  tools  are  necessarily  idle. 

XI.  Operation  and  Testing  of  Factory  Installations. 

1.  The  Generating  Plant.  As  far  as  practicable,  each  unit 
should  be  operated  at  its  normal  capacity — additional  units  to 
be  switched  in  as  may  be  required  by  the  manufacturing  con- 
ditions. 

2.  The  Motors.  Karely  the  case  that  any  machine  or  tool  is 
started  from  rest  with  full  load  upon  it.  Motors  may  be  started 
best  under  the  usual  friction,  or  light  loads  on  the  machines,  as 
in  the  belt  systems.  When  the  machine  is  brought  up  to  proper 
speed,  work  may  be  thrown  on  to  it;  In  this  respect  the  practi- 
cal operation  of  an  individual  electric  drive  follows  closely  that 
of  the  belt  system. 

It  is  always  possible  to  tell  exactly  what  is  going  on  in  an 
electric  drive,  both  in  kind  and  amount  of  useful  work,  as  well 
as  in  matter  of  wastes  and  losses.  Power  measurements  are 
made  at  any  point  by  ammeter  and  voltmeter,  or  by  a wattmeter 
alone.  A special  test  motor  of  known  performance  lends  itself 
admirably  to  comparative  tests  of  the  performance  of  machines 
and  tools  under  various  conditions.  Workmen  may  know  at 
any  moment  whether  they  are  driving  tools  or  machine  to  best 
advantage  for  maximum  output  at  best  speeds. 

The  definite  power  required  for  definite  work  may  be  deter- 
mined and  charged  to  each  machine,  tool,  or  piece  of  work,  and 
so  make  up  the  shop  cost  of  production  more  exactly  than  by 
any  other  system.  The  power  lost  in  friction  of  individual  ma- 
chines when  running  empty  may  be  obtained  with  equal  facility 


18  REQUIREMENTS  OF  ELECTRICITY  IN  MANUFACTURING  WORK. 


and  compared  with  that  required  in  doing  useful  work.  It  will 
he  found  that  the  latter  increases  almost  directly  as  the  resist- 
ance being  overcome  by  the  machine  in  its  operation  under 
working  conditions.  The  power  required  by  the  work  is  a small 
per  cent. 'of  the  total  power  delivered  to  the  machine. 


